1) Field of the Invention
This invention relates to a process and apparatus for treating water--such as underground water, drinking water or effluent--contaminated with a toxic organochlorine solvent such as chloroform, trichloroethylene, tetrachloroethylene or methylchloroform so as to decompose the organochlorine solvent contained in the water.
2) Description of the Prior Art
For the purification of water contaminated with trichloroethylene out of organochlorine solvents, there are various known processes such as aeration, adsorption on activated carbon, decomposition by the Fenton's reagent, oxidative decomposition by hydrogen peroxide, oxidative decomposition by ozone, oxidative decomposition by both ozone and hydrogen peroxide, decomposition by illumination of ultraviolet rays, and decomposition by ultraviolet rays in the co-existence of ozone and hydrogen peroxide.
These processes, however, have not been systematically studied with respect to organochlorine solvents other than trichloroethylene. Further, there is practically no report on the decomposition of methylchloroform contained in water.
The aeration process comprises blowing a great deal of air into water to drive out any high-volatility organochlorine solvent or solvents into the atmosphere, so that it involves the potential danger that a new problem of environmental pollution may arise.
The activated carbon adsorption process eliminates organochlorine solvent or solvents from contaminated water by simply adsorbing the solvent or solvents on activated carbon. An additional process is therefore required for the decomposition of the organochlorine solvent or solvents.
The decomposition process making use of the Fenton's reagent employs ferrous and ferric salts in large amounts, resulting in the occurrence of sludge. Disposal of the sludge is cumbersome.
It is also known to decompose chloroform and/or trichloroethylene, which is contained in water, in the presence of titanium oxide as a photo-oxidative catalyst (J. of Catalysis, 82, 418-423, 1983; J. of Catalysis, 82, 404-417, 1983; Environ. Sci. Technol., 17(10), 628-631, 1983). Titanium oxide employed in these processes is not a ferroelectric substance. Moreover, these processes use neither ozone nor hydrogen peroxide and the decomposition velocity of such organochlorine solvents is slow.
The remaining processes are all accompanied by the problems that the efficiency of decomposition of organochlorine solvents is poor and the operation cost is high.
Further, there is no known process for the efficient decomposition of methylchloroform contained in water.